[PATCH v2] ppc/pnv: generate dtb after machine initialization is complete

[Shivang Upadhyay <shivangu@linux.ibm.com>]

Currently, the machine dtb is generated in pnv_init(), before all devices
are fully initialized. This can result in an incomplete dtb for the system,
as seen in bug [1].

Fix this by deferring dtb generation until machine initialization is complete,
using the machine_init_done_notifier hook.

[1] https://lore.kernel.org/all/20260323231612.GA2637687@ax162/

Cc: Aditya Gupta <adityag@linux.ibm.com>
Cc: Harsh Prateek Bora <harshpb@linux.ibm.com>
Cc: BALATON Zoltan <balaton@eik.bme.hu>
Cc: qemu-stable@nongnu.org
Reported-by: Nathan Chancellor <nathan@kernel.org>
Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Fixes: a16d4c2f162a86d ("ppc/pnv: fix dumpdtb option")
Signed-off-by: Shivang Upadhyay <shivangu@linux.ibm.com>

---
Changes:

v2:
* moved pnv->bmc initialization to pnv_machine_init_done.

v1:
* https://lore.kernel.org/all/20260324135026.247418-1-shivangu@linux.ibm.com/
---
 hw/ppc/pnv.c         | 58 +++++++++++++++++++++++++-------------------
 include/hw/ppc/pnv.h |  2 ++
 2 files changed, 35 insertions(+), 25 deletions(-)

diff --git a/hw/ppc/pnv.c b/hw/ppc/pnv.c
index 7e54b6bc60..524563dcfc 100644
--- a/hw/ppc/pnv.c
+++ b/hw/ppc/pnv.c
@@ -748,31 +748,10 @@ static void pnv_powerdown_notify(Notifier *n, void *opaque)
 
 static void pnv_reset(MachineState *machine, ResetType type)
 {
-    PnvMachineState *pnv = PNV_MACHINE(machine);
-    IPMIBmc *bmc;
     void *fdt;
 
     qemu_devices_reset(type);
 
-    /*
-     * The machine should provide by default an internal BMC simulator.
-     * If not, try to use the BMC device that was provided on the command
-     * line.
-     */
-    bmc = pnv_bmc_find(&error_fatal);
-    if (!pnv->bmc) {
-        if (!bmc) {
-            if (!qtest_enabled()) {
-                warn_report("machine has no BMC device. Use '-device "
-                            "ipmi-bmc-sim,id=bmc0 -device isa-ipmi-bt,bmc=bmc0,irq=10' "
-                            "to define one");
-            }
-        } else {
-            pnv_bmc_set_pnor(bmc, pnv->pnor);
-            pnv->bmc = bmc;
-        }
-    }
-
     fdt = machine->fdt;
     cpu_physical_memory_write(PNV_FDT_ADDR, fdt, fdt_totalsize(fdt));
 }
@@ -984,6 +963,37 @@ static uint64_t pnv_chip_get_ram_size(PnvMachineState *pnv, int chip_id)
     return chip_id == 0 ? 1 * GiB : QEMU_ALIGN_DOWN(ram_per_chip, 1 * MiB);
 }
 
+static void pnv_machine_init_done(Notifier *notifier, void *data)
+{
+    PnvMachineState *pnv = container_of(notifier, PnvMachineState, machine_init_done);
+    MachineState *machine = MACHINE(pnv);
+    IPMIBmc *bmc;
+
+    /*
+     * The machine should provide by default an internal BMC simulator.
+     * If not, try to use the BMC device that was provided on the command
+     * line.
+     */
+    bmc = pnv_bmc_find(&error_fatal);
+    if (!pnv->bmc) {
+        if (!bmc) {
+            if (!qtest_enabled()) {
+                warn_report("machine has no BMC device. Use '-device "
+                            "ipmi-bmc-sim,id=bmc0 -device isa-ipmi-bt,bmc=bmc0,irq=10' "
+                            "to define one");
+            }
+        } else {
+            pnv_bmc_set_pnor(bmc, pnv->pnor);
+            pnv->bmc = bmc;
+        }
+    }
+
+    if (!machine->fdt) {
+        machine->fdt = pnv_dt_create(machine);
+        _FDT((fdt_pack(machine->fdt)));
+    }
+}
+
 static void pnv_init(MachineState *machine)
 {
     const char *bios_name = machine->firmware ?: FW_FILE_NAME;
@@ -1244,10 +1254,8 @@ static void pnv_init(MachineState *machine)
         pmc->i2c_init(pnv);
     }
 
-    if (!machine->fdt) {
-        machine->fdt = pnv_dt_create(machine);
-        _FDT((fdt_pack(machine->fdt)));
-    }
+    pnv->machine_init_done.notify = pnv_machine_init_done;
+    qemu_add_machine_init_done_notifier(&pnv->machine_init_done);
 }
 
 /*
diff --git a/include/hw/ppc/pnv.h b/include/hw/ppc/pnv.h
index 24f8843a40..90028f974d 100644
--- a/include/hw/ppc/pnv.h
+++ b/include/hw/ppc/pnv.h
@@ -111,6 +111,8 @@ struct PnvMachineState {
 
     bool         big_core;
     bool         lpar_per_core;
+
+    Notifier     machine_init_done;
 };
 
 PnvChip *pnv_get_chip(PnvMachineState *pnv, uint32_t chip_id);
-- 
2.53.0